A voice coil motor (VCM) is a relatively simple motor. Specifically, a linear voice coil motor is widely used in the optical field, such as an auto focus module of a camera of a cell phone. For clarity, a moving part in the voice coil motor is referred to as a rotor assembly, and a relatively fixed part is referred to as a stator assembly hereinafter.
A basic structure of the voice coil motor shown in FIG. 1 generally includes a stator 11, a rotor 12 and an elastic connecting piece 13. The elastic connecting piece connects the rotor and the stator. A load (not shown) is fixedly mounted at the rotor. In FIG. 1, the stator is a permanent magnet, and the rotor assembly includes a drive coil 123 wound on the rotor. After the drive coil is supplied with power, the rotor is linearly moved under the action of the magnetic field of the stator. A movement of the rotor in an opposite direction may be achieved by supplying a reverse current to the drive coil or utilizing the restoring force of the elastic connecting piece. In other examples, it is also possible that the rotor is a permanent magnet and the drive coil is a part of the stator assembly.
The voice coil motor with the aforesaid structure may precisely position the location of the load, for example moving a focus lens to a desired position, by means of balance between the electromagnetic force generated by the drive coil and the elastic force of the elastic connecting piece. In general, the elastic force of the elastic connecting piece is proportional to the displacement thereof in a working range, which leads to that the larger the displacement of the rotor, the larger the electromagnetic force required, and the larger the current of the drive coil. When the rotor needs to be stayed at a fixed position, for example a position for focusing, for a long time, the current of the drive coil needs to be maintained for a long time, which leads to a larger static holding power consumption of the voice coil motor.